Herein, we report a new application of the prize-winning Grubbs catalysts, which have been widely applied for olefin metathesis, for hydrogen production from aqueous-phase methanol reforming under easily achievable conditions (1 atm, <100 °C) with negligible CO formation. Out of the catalysts tested, the best turnover frequency (158 h–1) and turnover number (11424, 72 h) were both achieved with a third-generation Grubbs catalyst (G-III). The best TOF was achieved with G-III and is competitive when compared with some of the best results reported (Chem. Rev.2018118372433). Also, G-III is found to be a versatile catalyst for the dehydrogenation of ethanol and formic acid. Mechanistic studies and DFT calculations shed light on the reaction mechanism, which involves an unusual substrate (solvent)-assisted six-membered-ring (σ-bond) metathesis pathway. This work should open up new opportunities in catalyst design in connection with the hydrogen economy and, more generally, with the development of clean and renewable energies.

on the occasion of her 10th founding anniversary.

A series of ruthenium alkylidene complexes were adopted to catalyze aqueous-phase reforming of ethanol for H 2 production at readily achievable temperatures (<100 °C). The best results were obtained using (SIMes)Ru(PCy 3 )(3-methyl-2butenylidene)Cl 2 (SIMes, 1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-ylidene; PCy 3 , tricyclohexylphosphine) with a fiveday reaction producing a maximum turnover number (TON) of 47,295; this value is the second-largest one known for homogeneously catalyzed ethanol dehydrogenation. Kinetic experiments confirmed that the reforming process undergoes a secondorder reaction kinetics, with both ethanol and water contributing to H 2 production. Analyses of the reaction mixture using an in situ 1 H NMR experiment revealed a possible intermediate coordinated with a hydride ligand, based on which and previous work a plausible mechanism was proposed.

Hydrogen (H2) production by aqueous-phase reforming of liquid organic hydrogen carriers such as methanol, ethanol, and formic acid has attracted much recent interest as it offers a safe and convenient...